In recent years, several different groups of animal viruses have been subjected to genetic manipulation either by homologous recombination or by direct engineering of their genomes. The availability of reverse genetics systems for both DNA and RNA viruses has created new perspectives for the use of recombinant viruses as vaccines, expression vectors, anti-tumor agents, gene therapy vectors, and drug delivery vehicles.
For example, many viral-based expression vectors have been deployed for expression of heterologous proteins in cultured recombinant cells. For example, the application of modified viral vectors for gene expression in host cells continues to expand. Recent advances in this regard include further development of techniques and systems for production of multi-subunit protein complexes, and co-expression of protein-modifying enzymes to improve heterologous protein production. Other recent progresses regarding viral expression vector technologies include many advanced genome engineering applications for controlling gene expression, preparation of viral vectors, in vivo gene therapy applications, and creation of vaccine delivery vectors.
However, there is still a need for more efficient methods and systems for expressing a gene of interest in heterologous expression systems, including multigenic expression systems for simultaneously producing of multiple heterologous polypeptides in cells and/or host organisms.